Can thinking that you are fat make you fat?

August 8, 2012

They're everywhere -- in magazines, on the Internet, on televisionpeople with super-thin bodies who are presented as having the ideal body form. But despite the increasing pressure to be thin, more and more of us are overweight. Now, researchers from the Norwegian University of Science and Technology (NTNU) have found that normal weight teens who perceive themselves as fat are more likely to grow up to be fat.

"Perceiving themselves as fat even though they are not may actually cause normal weight children to become obese as adults," says Koenraad Cuypers, a researcher at the Norwegian University of Science and Technology.

Cuypers and his colleagues at the Department of Public Health and General Practice in NTNU's Faculty of Medicine have looked at data from the Nord-Trøndelag Health Study (HUNT) to examine the obesity problem from a new angle: Theirs is the first study to look at the relationship between perceived weights and actual weights in a longitudinal study of teenagers and young adults.

A perpetual struggle for the ideal body

There are likely many different, and complex, reasons that explain why thinking you are fat as a teen even if you are not  may lead you to become fat when you are grown.

One explanation may be related to psychosocial stress, which can be associated with gaining weight around the waist. Under this scenario, the psychosocial stress related to having (or not having) an ideal body type, along with the perception of oneself as overweight, can result in weight gain.

"Another explanation may be that young people who see themselves as fat often change their eating habits by skipping meals, for example. Research has shown that dropping breakfast can lead to obesity," Cuypers says.

Additionally, following a diet that you cannot maintain over time will also be counterproductive, since the body strives to maintain the weight you had before you started the diet.

The researchers checked whether physical activity made a difference in the relationship between perceived and actual obesity. But they found that exercise could not compensate for the negative effect of feeling overweight at a young age.

Higher BMI, larger waist circumference

The health survey Young-HUNT1 was conducted from 1995-1997 and included 1196 normal weight teenagers of both sexes. Participants were later followed up in the Young-HUNT3 study, from 2006-2008, when they had grown to be between 24 and 30 years of age.

Half of the participants still had normal weights as adults. But among those who were overweight, the researchers found a clear difference:

The data showed that 59 percent of the girls who had felt fat as a teen became overweight in adulthood, as measured using body mass index, or BMI. If waist circumference was used as the measure of obesity, then the percentage of teens who initially perceived themselves as fat and later became overweight as adults was 78 percent.

In contrast, 31 percent of the girls who did not consider themselves fat during adolescence were found in the follow-up study to be overweight as measured using BMI. That number was 55 percent as measured by waist circumference.

Normal weight teens who rated themselves as fat in the initial HUNT study had a BMI in the follow-up HUNT study that was on average 0.88 higher than those who did not. They were also on average 3.46 cm larger as measured around the waist.

Similar studies have previously been conducted in normal weight adult men and women. These studies have also shown an increase in weight over time in those who perceived themselves as too fat.

Simple measures for normal weight

The study also shows that normal weight girls were more likely than boys to rate themselves as overweight: 22 percent of girls and nine percent of the boys saw themselves as fat in the first HUNT survey.

One explanation for this gender difference may be that the media's focus on looks increasingly targets girls rather than boys.

"Girls thus experience more psychosocial stress to achieve the ideal body," Cuypers says. "Society needs to move away from a focus on weight, and instead needs to emphasize healthy eating habits, such as eating regular and varied meals and eating breakfast. Good sleep habits are also an advantage. And by reducing the amount that teens are transported to and from school and recreational activities, teens might also be able to avoid getting a 'commuter belly'," Cuypers adds.

These kinds of measures can improve overall health, and can also be a help for teens who are in fact overweight, but who believe their weight is normal.

Role models, not super models

Cuypers believes that the relationship between perceived obesity and the development of obesity is something the school system and society as a whole must address in order to reverse the trend and reduce societal problems associated with obesity.

"The weight norms for society must be changed so that young people have a more realistic view of what is normal. In school you should talk to kids about what are normal body shapes, and show that all bodies are beautiful as they are. And, last but not least: The media must cease to emphasize the super model body as the perfect ideal, because it is not." Cuypers says.

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